1. Field of the Invention
The present invention relates to the encoding of computer-generated images, and more particularly to the encoding of 3D scenes utilizing 3D rotations and 3D normals.
2. Discussion of the Background
The phrase "computer-generated images" encompasses an expanding area of video technology. Originally the term was often equated with simple text images or 2D images; however, the phrase now encompasses any type of digitally encoded video stream. The Motion Pictures Expert Group (MPEG) was formed to investigate the technologies required for the encoding and decoding of image streams. The resulting standard (now referred to as "MPEG-1") has served as a basis for two additional MPEG standards: MPEG-2 and MPEG-4. MPEG-4 is a standard that is "in progress" and forms the basis for the present invention. The final committee drafts are ISO/IEC FCD 14496-1 MPEG-4 Systems and -2 MPEG-4 Visual, the contents of the final committee drafts are incorporated herein by reference.
The draft standard departs from the single stream-based model of video and raises the focus to a series of streams that act in concert. One portion of the standard is the Binary Format for Scenes (also known as "BIFS"). This format allows the description of 3D objects and their motion and provides the ability for greater interaction with that portion of the video stream. The draft standard, however, does not directly provide a topologically coherent quantization scheme that supports a compensation process.
The representation of rotations with quaternions is known to be used in 3D computing, but not in the context used in the present invention. One known use is in the Cosmo viewer in which quaternions are used internally to interpolate between two rotations to avoid rendering artifacts.